Prevalence and characterization of non-sicca onset primary Sjögren syndrome with interstitial lung involvement

Primary Sjögren syndrome (pSS)-related interstitial lung disease (ILD) involved about 10-20% of patients. In 20% of cases, ILD can be diagnosed before pSS; anyway, few studies have investigated the frequency of ILD as the first clinically relevant manifestation of pSS, generally referred to retrospective studies. Aim of our prospective study was to describe prevalence, clinical, serological, and instrumental features of non-sicca onset pSS patients with interstitial lung involvement. During a period of 48 months, all consecutive patients diagnosed as pSS were enrolled. For all patients, the reason for the first visit was recorded. When present, ILD was categorized as definite, possible, or inconsistent with usual interstitial pneumonia (UIP) pattern, according to the current criteria. ILD was the main presenting symptom in 13/77 new diagnoses of pSS patients; in particular, 6/13 patients were initially diagnosed as idiopathic ILD, and only later developed clinical manifestations suggestive for pSS; ILD-pSS patients were older than others and showed a higher EULAR primary Sjögren's syndrome disease activity index. A radiologic definite or possible UIP pattern was detected in 12/13 pSS. For the first time, we prospectively observed a prevalence of 16.8% of non-sicca onset pSS patients with ILD. Interestingly, UIP pattern was the most frequently detected, while typical autoantibodies were often absent. These features stressed the importance of differential diagnosis in the first stage of the disease, considering the possible poorer prognosis in this subgroup of patients. Multidisciplinary approach is crucial for a correct and early diagnosis, at both onset and follow-up.